The most common means of recovering a desired mineral from a metal sulfide ore is by a procedure that includes froth flotation (Froth Flotation: A Century of Innovation, Fuerstenau, et al. eds., Soc. Mining, Metallurgy and Exploration, 2007). Typically, ores are suspended in water and ground using milling equipment to the “liberation size,” i.e., the largest particle size which exposes the desired mineral to the action of flotation reagents (usually about 50-200 μm). The ground ore forms a pulp which is fed to flotation cells that are typically arranged in banks of roughers, scavengers and cleaners.
During froth flotation, air is introduced into the pulp as fine bubbles which provide a surface for the attachment of relatively hydrophobic minerals. These minerals then rise with the bubbles to the surface of flotation cells and are removed. The hydrophilic gangue particles are less attracted to the air bubbles and therefore tend to be left behind in the pulp. Frothers (such as pine oil, polyglycols and polyoxyparafins) and pH modifiers (such as CaO, Na2CO3, NaOH or H2SO4, HCl) may be used to improve separations. Collectors (e.g., xanthates, carbonates and fatty acids) may also be introduced to help promote the attachment of minerals to air bubbles. In more complicated flotation circuits, the minerals may be either collected with the froth product (known as the overflow) or with the tail, or underflow. In addition, scavenger, cleaner, and re-cleaner cells, with or without an intermediate re-grinding step, may also be employed.
The proper oxygenation of pulp is an important parameter in the flotation of complex metal sulfide ores (Surface Chemistry of Froth Flotation, Jan Leja, Plenum Press (1982)). For example, it has been reported that conditioning of ore slurries with oxidants such as hydrogen peroxide can be used as part of a process to separate a desired copper mineral from unwanted iron sulfide, as well as from other copper-containing minerals (U.S. Pat. Nos. 5,110,455 and 5,295,585). However, incorrect oxygen levels may adversely affect separations and recovery. Thus, the conditions under which oxygenation is performed is important to the ultimate success of these enrichment procedures.